In connection with our investigation of the independent and solid axle suspension systems for four wheel drive vehicles, which are disclosed in patent application Ser. Nos. 14/059,062 and 14/324,105, respectively, we sought a shock absorber with unique compressed length, extended length properties. A survey of the art uncovered one feature common to virtually all shock absorbers—the extended length is less than twice the compressed length. This feature results from the inherent design of a shock absorber, namely, a single shaft that travels into/out of a single working tube. The length of the shaft defines the shock's travel. A shaft length of 6-8 inches is common and adequate for most vehicles. Such shocks have a relatively short compressed length thereby easing installation on production-based vehicles. However, in the off-road environment, a vehicle routinely encounters trail obstacles—e.g., boulders, fallen trees, ravines, cliffs—that exceed the limit of shock travel. To contend with such obstacles, engineers have designed long travel shocks with 12 inches or more of shaft length. These shocks require a working tube length at least equal to their shaft length. To account for the working piston, the working tube length of these shocks can be several inches longer than their shaft length—at least 14 inches or more. Such shocks have a relatively long compressed length thereby hampering installation on production-based vehicles. Typical methods of dealing with long travel shock issues include allowing the upper portion of the shock to protrude through the hood of the vehicle (for front shocks), or to protrude into the bed or trunk of the vehicle (for rear shocks). Such intrusive methods of installation are not practical for our needs, nor for production-based vehicles. Rather, our attention was drawn to a concept for a shock absorber whose extended length is greater than twice its compressed length. Moreover, given that many types of production-based vehicles are routinely used in industries that involve off-road driving, e.g., construction, farming and ranching, mining, forestry, gas and oil exploration, then automobile manufacturers and numerous other industries would greatly benefit from a long travel shock that could be easily installed on production-based vehicles.
A technique for resolving long travel shock issues would involve a shock with a relatively short compressed length and a relatively long travel length. Conceptually, this technique would require a shock that could extend several times greater than just twice its compressed length. A shock whose shaft would push down completely into a working tube of the same length thus giving a fully compressed shock; and, then push out of and seemingly grow several times greater than the working tube thus giving a fully extended shock whose length is several times greater than its compressed length.
In principle, a shock whose shaft was segmented like a simple telescope or spyglass could extend many times beyond its original compressed length. This principle refers to a design that consists of more than one independent shock-unit operating in series where the working tube for one shock-unit serves as the shaft for the next larger shock-unit, and so on. This design would have one shock-unit pushing down into the next larger one, and so on, so that by ignoring end caps and working pistons, the length of just one (the largest) working tube is representative of the shock's compressed length while the number of shock-units used in the shock's construction is representative of its extended length—e.g., three shock-units could extend three times beyond the compressed length, four shock units could extend four times beyond the compressed length, and so on—in effect, a shock within a shock. This shock within a shock design is ideally suited for our needs, and for installation on production-based vehicles thereby fulfilling the need of numerous industries that would benefit from a long travel shock with a short compressed length.
During the course of our investigation, it was brought to our attention that the shock within a shock design is known in the art as a multiple stage shock absorber. Therefore, our investigation was re-focused on developing a process for constructing this shock absorber. The construction process comprises novel means that are absent in the art, including means for adding stages to the shock, determining various lengths for the shock, and determining various spring rates for the shock.